LI-7 NUCLEAR-MAGNETIC-RESONANCE STUDY FOR THE DETERMINATION OF LI-SY5Y CELLS( PROPERTIES IN NEUROBLASTOMA SH)

Lithium has been used clinically in the treatment of manic depression, However, its pharmacologic mode of action remains unclear, Characteri stics of Li+ interactions in red blood cells (RBCs) have been identifi ed. We investigated Li+ interactions on human neuroblastoma SH-SY5Y ce lls by developing a novel Li-7 NMR method that provided a clear estima tion of the intra- and extracellular amounts of Li+ in the presence of the shift reagent thulium-1,4,7,10-tetrazacyclododecane-N, N',N '', N '''-tetramethylene phosphonate (HTmDOTP4-). The first-order rate const ants of Li+ influx and efflux for perfused, agarose-embedded SH-SY5Y c ells in the presence of 3 mM HTmDOTP4- were 0.055 +/- 0.006 (n = 4) an d -0.025 +/- 0.006 min(-1) (n = 3), respectively, Significant increase s in the rate constants of Li+ influx and efflux in the presence of 0. 05 mM veratridine indicated the presence of Nai channel-mediated Li+ t ransport in SH-SY5Y cells. Li-7 NMR relaxation measurements showed tha t Li+ is immobilized more in human neuroblastoma SH-SY5Y cells than in human RBCs.